U.S. patent number 10,493,759 [Application Number 16/131,076] was granted by the patent office on 2019-12-03 for devices for foil transfer.
This patent grant is currently assigned to ROLAND DG CORPORATION. The grantee listed for this patent is Roland DG Corporation. Invention is credited to Sho Matsumoto, Fumihiro Takahashi, Takeshi Tozuka.
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United States Patent |
10,493,759 |
Matsumoto , et al. |
December 3, 2019 |
Devices for foil transfer
Abstract
A foil transfer device includes a light emitter that emits
light, a driver that causes scanning to be performed with the light
by moving one or both of an irradiator and a substrate relative to
each other, the irradiator casting the light emitted by the light
emitter, and a controller that causes the light emitter to change
power of the light according to a velocity indication value during
at least one of an acceleration period from a time when at least
one of the irradiator and the substrate begins to move to a time
when a velocity thereof becomes constant and a deceleration period
from a time when the velocity is constant to a time when at least
one of the irradiator and the substrate stops.
Inventors: |
Matsumoto; Sho (Hamamatsu,
JP), Takahashi; Fumihiro (Mahamatsu, JP),
Tozuka; Takeshi (Hamamatsu, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Roland DG Corporation |
Hamamatsu-shi, Shizuoka |
N/A |
JP |
|
|
Assignee: |
ROLAND DG CORPORATION
(Shizuoka, JP)
|
Family
ID: |
65807082 |
Appl.
No.: |
16/131,076 |
Filed: |
September 14, 2018 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20190092010 A1 |
Mar 28, 2019 |
|
Foreign Application Priority Data
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|
|
|
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Sep 22, 2017 [JP] |
|
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2017-182503 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B41M
5/46 (20130101); B41J 2/14104 (20130101); B41M
5/382 (20130101); B41J 2/442 (20130101); B41J
2002/0052 (20130101) |
Current International
Class: |
B41M
5/46 (20060101); B41M 5/382 (20060101); B41J
2/44 (20060101); B41J 2/14 (20060101); B41J
2/005 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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5926083 |
|
May 2016 |
|
JP |
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2016-215599 |
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Dec 2016 |
|
JP |
|
Primary Examiner: Nguyen; Lamson D
Attorney, Agent or Firm: Keating & Bennett, LLP
Claims
What is claimed is:
1. A foil transfer device to transfer a foil film to a substrate
into a predetermined shape by scanning with light, the substrate on
which the foil film is provided, the foil transfer device
comprising: a light emitter that emits the light; a driver to cause
the scanning to be performed with the light by moving one or both
of an irradiator and the substrate relative to each other, the
irradiator casting the light emitted by the light emitter; and a
controller that controls the light emitter so as to allow the light
emitter to change power of the light according to a velocity
indication value during at least one of an acceleration period from
a time when at least one of the irradiator and the substrate begins
to move to a time when a velocity thereof becomes constant and a
deceleration period from a time when the velocity is constant to a
time when at least one of the irradiator and the substrate
stops.
2. The foil transfer device according to claim 1, wherein the
controller controls the light emitter so as to allow the light
emitter to change the power of the light by analog control.
3. The foil transfer device according to claim 1, wherein the
controller controls the light emitter so as to allow the light
emitter to change the power of the light by PWM control.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of priority to Japanese Patent
Application No. 2017-182503 filed on Sep. 22, 2017. The entire
contents of this application are hereby incorporated herein by
reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to foil transfer devices.
2. Description of the Related Art
Conventionally, characters, patterns, and graphics are often
printed onto a substrate such as paper or leather by transferring a
foil film such as metallic foils and films with a pigmented coating
to a surface of the substrate. Printing images such as characters
with foil films can improve visibility and decorativeness.
Laser beams can be used as a means to transfer foil films to a
substrate. For example, Japanese Patent No. 5926083 discloses a
transfer method that includes a lapping step for lapping a
composite of a transfer layer and an adhesive layer over the
substrate, and a laser irradiation step for irradiating the
composite with a laser beam to transfer the transfer layer to the
substrate. Laser beams are casted by a laser irradiation unit. The
laser irradiation unit is configured to be able to scan the
composite using driving means and can irradiate a transfer image
(transfer region) with a laser beam.
Here, an example is described where a straight line, with start
point "S" and end point "E," is transferred to a substrate C by
scanning, with a laser beam, the substrate C on which a foil film F
is laid. In this conventional foil application methods, the laser
beam is emitted by applying an electric current to a laser emitter.
Then, an irradiation unit (for example, a laser irradiation unit in
Japanese Patent No. 5926083) that casts the laser beam emitted by
the laser emitter is linearly moved from the start point "S" to the
end point "E" at a predetermined velocity. By adjusting the amount
of electric current flowing through the laser emitter, the power of
the laser beam can be varied.
FIG. 6 is a diagram showing transitions of a velocity indication
value supplied to the irradiation unit and an electric current
value flowing through the laser emitter used in a conventional foil
application method. The velocity indication value is for moving the
irradiation unit at a predetermined velocity or velocities. As can
be seen in FIG. 6, the velocity indication value gradually
increases during the acceleration of the irradiation unit and
gradually decreases during the deceleration of the irradiation
unit; therefore, the irradiation unit does not move at a constant
velocity during acceleration and deceleration.
On the contrary, as can be seen in FIG. 6, the electric current
value flowing through the laser emitter reaches a predetermined
value immediately once the acceleration of the irradiation unit
begins and drops to zero immediately as the irradiation unit stops;
therefore, the power of the laser beam was constant throughout the
entire movement of the irradiation unit.
Thus, in the conventional foil application methods, the power of
the laser beam is constant despite the non-constant traveling
velocities of the irradiation unit during acceleration or
deceleration and the foil film F will experience more heat.
Since certain areas of the foil film F that are not intended to be
transferred also receive the heat, the transferred area in the foil
film F becomes expanded, causing uneven transfer of the foil film F
(see FIG. 7).
Owing to this, foil transfer devices described in JP-A-2016-215599
control the laser beam so as not to irradiate the foil film with
the laser beam during the acceleration and deceleration in scanning
a light pen (corresponding to the aforementioned irradiation
unit).
SUMMARY OF THE INVENTION
Preferred embodiments of the present invention provide foil
transfer devices with each of which uneven transfer during
acceleration and deceleration of an irradiator that casts light is
able to be reduced.
A preferred embodiment of the present invention provides a foil
transfer device to transfer a foil film to a substrate into a
predetermined shape by scanning with light, the substrate on which
the foil film is provided, the device including a light emitter
that emits the light; a driver to perform the scanning with the
light by moving one or both of an irradiator and the substrate
relative to each other to cause the irradiator to cast the light
emitted by the light emitter; and a controller that controls the
light emitter so as to cause the light emitter to change power of
the light according to a velocity indication value during at least
one of an acceleration period from a time when at least one of the
irradiator and the substrate begins to move to a time when a
velocity thereof becomes constant and a deceleration period from a
time when the velocity is constant to a time when at least one of
the irradiator and the substrate stops.
Other features of preferred embodiments of the present invention
will be apparent from the description of preferred embodiments in
the specification.
According to preferred embodiments of the present invention, it is
possible to reduce uneven transfer during the acceleration and
deceleration of the irradiator that casts light.
The above and other elements, features, steps, characteristics and
advantages of the present invention will become more apparent from
the following detailed description of the preferred embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram showing a foil transfer device
according to a first preferred embodiment of the present
invention.
FIG. 2 is a schematic diagram showing an irradiator according to
the first preferred embodiment of the present invention.
FIG. 3 is a diagram showing a relationship between a velocity
indication value and an electric current value according to the
first preferred embodiment of the present invention.
FIG. 4 is a diagram showing a substrate with foil applied by the
foil transfer device according to the first preferred embodiment of
the present invention.
FIG. 5A is a diagram showing a relationship between a velocity
indication value and an electric current value according to a
second preferred embodiment of the present invention.
FIG. 5B is a diagram showing a relationship between the velocity
indication value and the electric current value according to the
second preferred embodiment of the present invention.
FIG. 6 is a diagram showing a relationship between a velocity
indication value and an electric current value according to a
conventional art.
FIG. 7 is a diagram showing a substrate with foil applied by a foil
transfer device according to a conventional art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Preferred Embodiment
Referring to FIGS. 1 to 4, a foil transfer device 1 according to a
first preferred embodiment of the present invention is
described.
The foil transfer device 1 according to this preferred embodiment
transfers a foil film F to a substrate C into a predetermined shape
by scanning, with a laser beam, the substrate C on which the foil
film F is laid. As shown in FIG. 1, the foil transfer device 1
includes an operation interface 10, a table 11, a laser emitter 12,
an irradiator 13, a driver 14, and a controller 15. The foil
transfer device 1 is connected to an external computer 2 such that
they can communicate with each other. The foil transfer device 1
may be realized partially or completely by the functioning of the
computer 2.
The computer 2 generates data about scanning paths along a
predetermined shape (such as a contour of a character) to be
transferred to the substrate C and transmits the data to the foil
transfer device 1. A personal computer may be used as the computer
2. A processing operation to create the scanning path is performed
using a predetermined program installed on the computer 2
beforehand.
The operation interface 10 enables a user to enter various inputs
to the foil transfer device 1. The operation interface 10 may be a
user interface including a device such as a display on which
results of processing by the foil transfer device 1 are displayed.
Further, the computer 2 may define and function as the operation
interface 10.
The table 11 supports the substrate C placed thereon. The table 11
according to this preferred embodiment is secured to the main body
of the foil transfer device 1. The surface (i.e., the transfer
surface) of the substrate C on which an object such as a character
is to be transferred is covered with the foil film F. An adhesive
layer may be provided between the foil film F and the substrate
C.
The laser emitter 12 emits a laser beam. For the laser emitter 12,
a semiconductor laser with a wavelength of 450 nm and maximum power
of 1 W, for example, can be used. The laser emitter 12 is not
limited to a semiconductor laser and a solid-state laser or a
gas-state laser may also be used. By applying a predetermined
electric current to the laser emitter 12, a laser beam is emitted
from the laser emitter 12. By adjusting the electric current
flowing through the laser emitter 12, power of the laser beam is
able to be controlled (details are described later). The laser
emitter 12 according to this preferred embodiment is an example of
the "light emitter."
The irradiator 13 casts the laser beam emitted by the laser emitter
12. The irradiator 13 is movable in three directions perpendicular
to each other (i.e., back and forth, side to side, and
vertical).
The irradiator 13 according to this preferred embodiment includes
an optical fiber 13a and a housing 13b (see FIG. 2). The optical
fiber 13a is connected to the laser emitter 12 and transmits the
laser beam emitted by the laser emitter 12. The laser beam is
emitted out of an output end 13c of the optical fiber 13a. The
housing 13b is a thin, elongated structure in which the optical
fiber 13a is held. The output end 13c of the optical fiber 13a is
flush or substantially flush with a bottom surface 13d of the
housing 13b. To the bottom surface 13d, a projection 13e is secured
to cover the output end 13c. In this preferred embodiment, the
projection 13e preferably has a hemispherical shape. The projection
13e is preferably made of a material that transmits a laser beam
that comes out of the output end 13c. Transfer of the foil film F
is performed by pressing the bottom surface 13d against the
substrate C via the foil film F and casting the laser beam in that
state. Further, in transferring a portion of the foil film F into a
certain shape, the irradiator 13 is able to move and irradiate the
substrate C with the laser beam while pressing the substrate C. The
projection 13e facilitates the application of the pressure, and its
hemispherical shape allows smooth motion of the irradiator 13 even
while pressing the substrate C.
It should be noted that the irradiator 13 may be disposed directly
on the main body of the foil transfer device 1 or indirectly via a
carriage that is movable in three directions. The irradiator 13 may
carry the laser emitter 12. Further, although the projection 13e in
FIG. 2 has a hemispherical shape, it may have any shape as long as
it protrudes from the bottom surface 13d. Further, in FIG. 2, the
configuration in which the projection 13e covers the output end 13c
has been described. However, the optical fiber 13a may pass through
the projection 13e and the output end 13c may be flush or
substantially flush with the bottom surface of the projection
13e.
The driver 14 causes performing of the scanning with the laser beam
by moving one or both of the irradiator 13 and the substrate C
placed on the table 11 relative to each other. In this preferred
embodiment, since the table 11 is secured to the main body of the
foil transfer device 1, the driver 14 causes the scanning to
performed with the laser beam by moving the irradiator 13.
The driver 14 includes a motor 14a. The motor 14a may be, for
example, a set of three motors that perform driving back and forth,
side to side, and in vertical directions. The motors 14a may be the
same or different in performance (e.g., electric current, torque,
rotational speed). The driver 14 according to this preferred
embodiment is able to move the irradiator 13 back and forth, side
to side, and up and down relative to the substrate C placed on the
table 11.
For example, the driver 14 moves the irradiator 13 to an
irradiation start position at which the irradiation of the
substrate C with the laser beam begins. Subsequently, the driver 14
moves the irradiator 13 downward and presses it against the
substrate C. The driver 14 then performs the scanning with the
laser beam by moving the irradiator 13. The relationship between
the power of the laser beam and the traveling velocity of the
irradiator 13 will be described later.
The controller 15 performs various controls of the foil transfer
device 1. The controller 15 of this preferred embodiment is
configured or programmed to control the driver 14 to move the
irradiator 13 in a predetermined direction. The controller 15
supplies, to the drive mechanism 14, data about scanning paths sent
from the computer 2 and a velocity indication value according to
the data about scanning paths. The drive mechanism 14 moves the
irradiator 13 at the velocity based on the velocity indication
value along the path designated by the data about scanning
paths.
The velocity indication value is used to determine the velocity at
which the irradiator 13 is moved. The controller 15 enters a
predetermined velocity indication value to the driver 14. Here, the
velocity indication value is different among during the
acceleration period, the deceleration period, and the period of
travel at a constant velocity. The acceleration period is a length
of time from a time when the irradiator 13 begins to move to a time
when the velocity thereof becomes constant. The deceleration period
is a length of time from the time when the velocity is constant to
a time when the irradiator 13 comes to a stop. The period of travel
at the constant velocity is a length of time during which the
irradiator 13 moves at a predetermined velocity (fixed
velocity).
The velocity indication value for the acceleration is set such that
the velocity gradually increases during a certain period. The
velocity indication value for the deceleration is set such that the
velocity gradually decreases during a certain period. The velocity
indication value for the period of travel at the constant velocity
is set such that the velocity is kept constant during a certain
period.
In addition, the controller 15 changes the power of the laser beam
emitted from the laser emitter 12 by controlling the laser emitter
12. Specifically, the controller 15 controls the laser emitter 12
so as to change the power of the laser beam according to the
velocity indication value, at least during the acceleration or
deceleration of the irradiator 13.
In this preferred embodiment, the controller 15 changes the power
of the laser beam by analog control, for example. FIG. 3 is a
diagram showing a relationship between the velocity indication
value to determine the velocity at which the irradiator 13 is moved
and an electric current value flowing through the laser emitter 12.
The controller 15 moves the irradiator 13 by supplying the velocity
indication value as shown in FIG. 3 to the driver 14 in time
series. With the velocity indication value shown in FIG. 3, the
irradiator 13 gradually accelerates according to the velocity
indication value (the acceleration period) and, after reaching a
certain velocity, moves at that velocity (the period of travel at
the constant velocity). The irradiator 13 then gradually
decelerates from the constant velocity (the deceleration period),
and finally stops. It should be noted that predetermined values are
set beforehand for the velocity at the constant velocity and the
power of the laser beam (i.e., the electric current value) during
the constant velocity.
The controller 15 changes the power of the laser beam by analog
control according to such velocity indication value. Specifically,
the controller 15 applies an analog voltage corresponding to the
velocity indication value to the laser emitter 12. An electric
current corresponding to the applied analog voltage flows through
the laser emitter 12.
For example, as shown in FIG. 3, when the velocity indicated by a
velocity indication value S.sub.1 is about 50% of the constant
velocity (i.e., the velocity indicated by a velocity indication
value S.sub.0) during acceleration, the controller 15 applies an
analog voltage to the laser emitter 12 such that the electric
current value becomes about 50% of a predetermined value A.sub.0.
An electric current (an electric current value A.sub.1 that is
equal to about 50% of the predetermined value A.sub.0) according to
the applied analog voltage flows through the laser emitter 12.
Then, the controller 15 performs a control so that the electric
current value becomes the predetermined value A.sub.0 at the time
point at which the mode switches from acceleration to constant
velocity (i.e., the velocity indicated by a velocity indication
value S.sub.0).
On the other hand, as shown in FIG. 3, when the velocity indicated
by a velocity indication value S.sub.2 is about 50% of the constant
velocity (i.e., the velocity indicated by a velocity indication
value S.sub.0) during deceleration, the controller 15 applies an
analog voltage to the laser emitter 12 such that the electric
current value becomes about 50% of the predetermined value A.sub.0.
An electric current (an electric current value A.sub.2 that is
equal to about 50% of the predetermined value A.sub.0) according to
the applied analog voltage flows through the laser emitter 12.
Then, the controller 15 performs a control so that the electric
current value becomes zero at the time point at which the velocity
indication value becomes zero.
In other words, the controller 15 controls the electric current
flowing through the laser emitter 12 so that it gradually increases
during the acceleration and gradually decreases during the
deceleration in a similar manner to the velocity indication value
(see, the periods designated as "Acceleration" and "Deceleration"
in FIG. 3). The velocity indication value is kept constant during
the period of travel at the constant velocity; therefore, the
controller 15 controls the electric current flowing through the
laser emitter 12 to be fixed during the period of travel at the
constant velocity (see the period designated as "Constant velocity"
in FIG. 3).
By allowing the electric current to flow in the manner described
above, the power of the laser beam gradually increases according to
the traveling velocity of the irradiator 13 during the acceleration
and the amount of heat transferred to the foil film F per unit time
is made constant. Likewise, the power of the laser beam gradually
decreases according to the traveling velocity of the irradiator 13
during the deceleration and the amount of heat transferred to the
foil film F per unit time is also made constant. Therefore, the
transferred foil film F never expands along the entire length of
transfer between the start point S and the end point E (see FIG.
4). In other words, the controller 15 according to this preferred
embodiment is able to provide analog control the laser output by
analogously changing the electric current flowing according to the
velocity indication value. Consequently, uneven transfer during
acceleration and deceleration is reduced.
In the above preferred embodiment, the laser emitter 12 that emits
the laser beam is used as the light emitter to transfer foil films,
but the present invention is not limited thereto. For example,
light emitting diodes can also be used as the light emitter.
Further, any other elements other than light emitting diodes can
also be used as the light emitter as long as they can change the
power of the light by changing the electric current applied
thereto.
While the above preferred embodiment describes an example where
only the irradiator 13 moves, the present invention is not limited
thereto. Specifically, foil films may be transferred by moving the
table 11 back and forth, side to side, and in vertical directions
relative to the fixed irradiator 13. In this case, the driver 14
drives the table 11 (for example, a motor moves the table 11 in
three directions). Alternatively, both of the irradiator 13 and the
table 11 may be moved.
As described above, the foil transfer device 1 according to this
preferred embodiment transfers the foil film F to the substrate C
into a predetermined shape by scanning, with light, the substrate C
on which the foil film F is laid. The foil transfer device 1
includes a light emitter that emits the light; the driver 14 to
cause the scanning to be performed with the light by moving one or
both of the substrate C and the irradiator 13 that casts the light
emitted by the light emitter relative to each other; and the
controller 15 that controls the light emitter so as to allow the
light emitter to change the power of the light according to the
velocity indication value during at least one of the acceleration
period from a time when at least one of the irradiator 13 and the
substrate C begins to move to a time when a velocity thereof
becomes constant and the deceleration period from a time when the
velocity is constant to a time when at least one of the irradiator
13 and the substrate C stops. The controller 15 of this preferred
embodiment controls the light emitter so as to allow the light
emitter to change the power of the light by analog control.
According to such a configuration, during the acceleration and/or
deceleration of the irradiator 13 and/or the substrate C, the power
of the light is gradually adjusted according to the velocity.
Therefore, the amount of heat transferred to the foil film F per
unit time is made constant. That is, according to the foil transfer
device 1 of this preferred embodiment, uneven transfer is able to
be prevented even during acceleration or deceleration.
Second Preferred Embodiment
Next, referring to FIGS. 5A and 5B, a foil transfer device 1
according to the second preferred embodiment is described.
Some laser emitters such as semiconductor lasers have a function of
not emitting a laser beam when the amount of applied electric
current is smaller than a predetermined value (i.e., emitting a
laser beam for the first time when a certain amount of electric
current flows).
Thus, with the analog control of the power of the laser beam during
acceleration and/or deceleration of the irradiator 13 as in the
case of the first preferred embodiment, it is possible that a laser
beam is not emitted at the time when acceleration of the irradiator
13 begins or at the time immediately before it comes to a stop. In
other words, it is possible that the power of the laser beam
required to transfer foil films cannot be obtained at the beginning
of the acceleration or just before the stop.
As a result, for example, in the case of transferring a foil film
as shown in FIG. 4, it is possible that a certain area that is
intended to be transferred is not transferred at the beginning of
the acceleration or just before the stop.
In this preferred embodiment, in order to solve this problem, an
example where the controller 15 controls the light emitter so as to
allow the light emitter to change the power of the laser beam by
PWM control is described. Since the configuration of the foil
transfer device 1 is the same as that of the first preferred
embodiment, details thereof are not described here.
The controller 15 according to this preferred embodiment produces a
laser beam by PWM control. The PWM control is a control method of
changing the power of the laser beam by pulse-controlling a
duration of applying the electric current while maintaining the
peak of the electric current value flowing through the laser
emitter 12. By performing the PWM control, the absolute value of
the electric current is made constant, so that the laser emitter 12
stably emits the laser beam from the beginning of acceleration.
FIG. 5A is a diagram showing a relationship between the velocity
indication value used to determine the velocity at which the
irradiator 13 is moved and an electric current value flowing
through the laser emitter 12. The controller 15 moves the
irradiator 13 by supplying the velocity indication value as shown
in FIG. 5A to the driver 14 in time series. With the velocity
indication value shown in FIG. 5A, the irradiator 13 gradually
accelerates according to the velocity indication value (the
acceleration period) and, after reaching a certain velocity, moves
at that velocity (the period of travel at the constant velocity).
The irradiator 13 then gradually decelerates from the constant
velocity (the deceleration period), and finally stops. As in the
first preferred embodiment, predetermined values are set beforehand
for the velocity at the constant velocity and the power of the
laser beam (i.e., the electric current value) during the constant
velocity.
The controller 15 changes the power of the laser beam by PWM
control according to such velocity indication value. Specifically,
the controller 15 supplies to the laser emitter 12 a PWM signal
with a predetermined frequency (several kHz to several tens of kHz)
with a certain duty ratio.
The duty ratio is determined based on the velocity indication
value. According to the velocity indication value, the controller
15 controls the duty ratio of the PWM signal to gradually increase
it during acceleration (see FIG. 5A). The gradual increase of the
duty ratio leads to gradual increase of the pulse width of the
electric current flowing through the laser emitter 12 in a
predetermined cycle. In addition, the controller 15 controls the
duty ratio of the PWM signal to gradually decrease it during
deceleration according to the velocity indication value (see FIG.
5A). The gradual reduction of the duty ratio leads to gradual
reduction of the pulse width of the electric current flowing
through the laser emitter 12 in a predetermined cycle. In the laser
emitter 12, an electric current corresponding to the supplied PWM
signal flows and a laser beam is emitted.
In other words, the controller 15 performs control, according to
the velocity indication value, to gradually increase the time
duration during which the electric current is applied during
acceleration and gradually reduce the time duration during which
the electric current is applied during deceleration, while
maintaining the electric current flowing through the laser emitter
12 to be constant (see, the periods designated as "Acceleration"
and "Deceleration" in FIG. 5A). The velocity indication value is
kept constant during the period of travel at the constant velocity;
therefore, the controller 15 controls the electric current flowing
through the laser emitter 12 to be fixed during the period of
travel at the constant velocity (see the period designated as
"Constant velocity" in FIG. 5A; the duty ratio is not changed).
It should be noted that, during the period of travel at the
constant velocity in FIG. 5A, the laser emitter 12 is controlled so
that an electric current continuously flows through it. On the
other hand, the controller 15 may perform control so that a pulsed
electric current flows with a certain duty ratio during the period
of travel at the constant velocity as in the case of the
acceleration and deceleration (see FIG. 5B).
As described above, by gradually changing the duty ratio of the PWM
signal during acceleration or deceleration of the irradiator 13
according to the velocity, the electric current flowing through the
laser emitter 12 per unit time is able to be made constant. That
is, the power of the laser beam per unit time given to the foil
film F is able to be made constant and the amount of heat
transferred to the foil film F is also made constant accordingly.
Even during accelerating or decelerating, the transferred foil film
F does not suffer from expansion as shown in FIG. 7. The controller
15 of this preferred embodiment is able to change the output of the
laser according to the velocity indication value by changing the
applied electric current according to the velocity indication value
by the PWM control. Therefore, it is possible to reduce uneven
transfer during acceleration and deceleration.
Further, by using the PWM control, the laser emitter 12 is capable
of emitting laser beams stably even at the time when acceleration
of the irradiator 13 begins or at the time immediately before it
comes to a stop. Therefore, the irradiation of the laser does not
become insufficient at the beginning of the acceleration or just
before the stop.
While preferred embodiments of the present invention have been
described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing from the scope and spirit of the present invention. The
scope of the present invention, therefore, is to be determined
solely by the following claims.
* * * * *